1. Technical Field
The present invention relates to a roller mill for coffee, a method for grinding coffee, and an application of a roller mill to grind coffee.
2. Background Information
Numerous roller mills are known from the prior art. It is also known to use roller mills to grind coffee.
Therein, these must be differentiated into roller mills with two rolls and so-called three-roll mills.
Three-roll mills, which are characterized in that they comprise three rollers with two grinding gaps found therebetween, can only be used for crushing viscous liquids or pastes, since the principle thereof is based on transporting the mass clinging to the bottom of the middle roller into the second grinding gap. Such three-roll mills are used for example to manufacture chocolate. Various rollers may be used therein. For example, metal or stone rollers are known in three-roll mills.
Since three-roll mills can only be operated with pasty masses, which cling onto the bottom of the middle roller, the grinding forces that arise herein are comparatively low. Homogenization, ventilation, dispersion and/or fine pulverization are achieved rather than grinding.
Also known are roller mills wherein only two rollers are used, which pull the pasty mass that is to be homogenized from a storage container bottom-up through the grinding gap. Here again it is essential that the pasty mass exhibit a certain adhesion to the grinding rollers. Homogenization, ventilation, dispersion and/or fine pulverization are also achieved rather than grinding.
Conventional rolling mills for grinding, however, are provided with two grinding rollers having a grinding gap found therebetween, and are loaded from above with the substance intended to be ground. Grinding rollers of such mills are usually made of metal. It is usual to use metal rollers in particular for grinding coffee. Such grinding rollers are usually structured on the surface. Grooves are preferably provided thereon. The loading operation is improved and the grinding is made more efficient by such grooves. It is also known to drive the grinding rollers such that the first grinding roller has a different rolling peripheral velocity from the second grinding roller. In such rolling mills for grinding, any adhesion of the substance to be ground should be directly prevented.
However the grooves and structures provided on the surface of the grinding rollers for a particularly efficient grinding of coffee are heavily stressed by dry grinding, and must be renewed at regular intervals, to at great expense.